1. Field of the Invention
The present invention relates to a transmission optical module used in optical link apparatus for data communications and the like.
2. Related Background Art
Transmission optical modules for converting electric signals into optical signals and sending out optical signals thus obtained to optical fibers have widely been use in optical communication systems such as data links and optical LANs using light as their information transmitting medium.
As shown in FIG. 8, a transmission optical module 100 comprises, within a mold resin, a light-emitting device assembly 101 incorporating a light-emitting device therein, a circuit board 104 on which an electronic device 102 for controlling the light-emitting device incorporated in the light-emitting device assembly 101 is mounted, and a lead frame 106 for mounting the circuit board 104. A plurality of connection pins 110 to 114 extend from a base 108 of the light-emitting device assembly 101. Among these connection pins 110 to 114, wires bond between the connection pin 112 connected to the anode of the light-emitting device and an anode pad 118 on the circuit board 104, and between the connection pin 110 connected to the cathode of the light-emitting device and a cathode pad 116 on the circuit board 104.
In such a conventional transmission optical module 100, a holding member 124 extending from the lead frame 106 holds the light-emitting device assembly 101 with a sleeve 126, whereby a source voltage is supplied to the light-emitting device within the light-emitting device assembly 101 through a path comprising the lead frame 106, holding member 124, sleeve 126, and light-emitting device in series.
The waveform of signal light outputted from the above-mentioned conventional transmission optical module, however, has not fully been stable. Therefore, it is an object of the present invention to provide a transmission module which can stabilize the waveform of signal light outputted therefrom.
The transmission optical module in accordance with the present invention comprises (1) a light-emitting device assembly having a light-emitting device, a case for accommodating the light-emitting device, and a connection pin extending outward from the case and electrically connected to an anode of the light-emitting device; (2) a circuit board, on which an electronic device for controlling the light-emitting device is mounted, and having a first pad to which a predetermined potential is applied and a second pad for supplying a source voltage; (3) a lead frame having a board mounting part for mounting the circuit board; and (4) wires bonding the connection pin to the first and second pads respectively.
This transmission optical module can stabilize the waveform of signal light outputted therefrom.
In the transmission optical module in accordance with the present invention, the source voltage may be supplied from the second pad alone. This can further stabilize the waveform of signal light outputted from the light-emitting device.
Preferably, in the transmission optical module in accordance with the present invention, the light-emitting device assembly, circuit board, and lead frame are encapsulated with a resin.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.